sczerwinski
commented
1 year ago Source: http://paulbourke.net/dataformats/obj/
The following syntax statements are listed in order of use.
cstype rat type
Free-form geometry statement.
Specifies the type of curve or surface and indicates a rational or
non-rational form.
rat is an optional argument.
rat specifies a rational form for the curve or surface type. If rat
is not included, the curve or surface is non-rational
type specifies the curve or surface type. Allowed types are:
bmatrix basis matrix
bezier Bezier
bspline B-spline
cardinal Cardinal
taylor Taylor
There is no default. A value must be supplied.
deg degu degv
Free-form geometry statement.
Sets the polynomial degree for curves and surfaces.
degu is the degree in the u direction. It is required for both
curves and surfaces.
degv is the degree in the v direction. It is required only for
surfaces. For Bezier, B-spline, Taylor, and basis matrix, there is
no default; a value must be supplied. For Cardinal, the degree is
always 3. If some other value is given for Cardinal, it will be
ignored.
bmat u matrix
bmat v matrix
Free-form geometry statement.
Sets the basis matrices used for basis matrix curves and surfaces.
The u and v values must be specified in separate bmat statements.
NOTE: The deg statement must be given before the bmat statements
and the size of the matrix must be appropriate for the degree.
u specifies that the basis matrix is applied in the u direction.
v specifies that the basis matrix is applied in the v direction.
matrix lists the contents of the basis matrix with column subscript
j varying the fastest. If n is the degree in the given u or v
direction, the matrix (i,j) should be of size (n + 1) x (n + 1).
There is no default. A value must be supplied.
NOTE: The arrangement of the matrix is different from that commonly
found in other references. For more information, see the examples
at the end of this section and also the section, "Mathematics for
free-form curves and surfaces."
step stepu stepv
Free-form geometry statement.
Sets the step size for curves and surfaces that use a basis
matrix.
stepu is the step size in the u direction. It is required for both
curves and surfaces that use a basis matrix.
stepv is the step size in the v direction. It is required only for
surfaces that use a basis matrix. There is no default. A value must
be supplied.
When a curve or surface is being evaluated and a transition from
one segment or patch to the next occurs, the set of control points
used is incremented by the step size. The appropriate step size
depends on the representation type, which is expressed through the
basis matrix, and on the degree.
That is, suppose we are given a curve with k control points:
{v , ... v }
1 k
If the curve is of degree n, then n + 1 control points are needed
for each polynomial segment. If the step size is given as s, then
the ith polynomial segment, where i = 0 is the first segment, will
use the control points:
{v ,...,v }
is+1 is+n+1
For example, for Bezier curves, s = n .
For surfaces, the above description applies independently to each
parametric direction.
When you create a file which uses the basis matrix type, be sure to
specify a step size appropriate for the current curve or surface
representation.
Hello, looks like cstype is not supported either. Here's some example OBJ code...
Not sure if you want to track that as a separate feature request.
Originally posted by @phillipsconsulting in https://github.com/sczerwinski/wavefront-obj-intellij-plugin/issues/470#issuecomment-1523910009